1. Field of the Invention
The present invention relates to a small hole electrical discharge machining method and a small hole electrical discharge machining apparatus, and an electrode inserting method with respect to an electrode guide of the small hole electrical discharge machining apparatus and an electrode inserting apparatus.
2. Description of the Related Art
In a conventional small hole electrical discharge machining apparatus, a stick-shaped, or pipe-shaped, slender electrode is rotatably supported by a main-axis portion. The main-axis portion is moved up/down by a feed screw that is rotated by a main-axis feed motor. By doing so, a lower end portion of the electrode is caused to come near to a workpiece and electrical discharge is caused to occur from the electrode. Thereby, a small hole is drilled. Then, an electrode guide member guides the lower end portion of the electrode to a proper accurate position.
Also, conventionally, to insert the stick-shaped (or pipe-shaped) slender electrode into the electrode guide member, a water jet jetted from an upper part of the stick-shaped electrode enveloping the water jet to feed the stick-shaped electrode up to the electrode guide member.
Incidentally, in the small hole electrical discharge machining that uses the stick-shaped electrode, in order to prevent a fusion-cutting of the electrode due to the electrical discharge, steps of the small hole electrical discharge machining method are executed in a state where the workpiece is placed within a working tank filled with a working liquid such as water or deionized water.
However, in the conventional small hole electrical discharge machining method and apparatus, dirty water from a worked portion enters an interior of the electrode guide, thereby the electrode guide got clogged or plugged. Hence, it is difficult to perform a long-term stable electrode feeding, and therefore continuous working was limited to one performed for approximately 2 hours or to one wherein the number of the worked holes was 1,000 pieces or so. Further, metal ions in the working liquid were reduced and the resulting material accreted onto the electrode guide. Resultantly, a hole of the electrode guide became small in diameter, and therefore, it is difficult to perform long-term stable electrode feeding.
Also, the conventional electrode inserting step inserting the electrode into the electrode guide, it is difficult to insert the electrode having a very small diameter such as 0.01 mm, 0.02 mm, and 0.03 mm.
The present invention has been made in order to solve the above-described problem and has an object to provide an electrode inserting method and apparatus that make more reliable the insertion of a very fine stick-shaped electrode into the electrode guide, and to provide a small hole electrical discharge machining method and apparatus that prevent entry of the dirty water, occurring within the working liquid, into the electrode guide, as well as reduction of the metal ions in the working and subsequent attachment of the resulting material onto the electrode guide, to enable stable feeding of the electrode and hence enhance the working accuracy.